Ultraviolet light

The ultraviolet light is a type of electromagnetic radiation . The light ultraviolet (UV) having a wavelength shorter than that of the light visible. The purple and violet colors have shorter wavelengths than other colors of light , and the ultraviolet light has even shorter wavelengths than the ultraviolet, so it is a kind of light more purple than purple or a light that goes beyond violet .


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  • 1 Features
  • 2 Impact on the environment
  • 3 The term black light
  • 4 Black Light Lamps
  • 5 Germicidal band of ultraviolet light
  • 6 Practical applications of ultraviolet light
  • 7 Germicidal power
  • 8 Advantages of UV light
  • 9 See also
  • 10 Source


The ultraviolet radiation is in the visible light and X – rays of the electromagnetic spectrum. Ultraviolet (UV) “light” has a wavelength between 380 and 10 nanometers . The wavelength of ultraviolet light is approximately 400 nanometers (4,000 Å). Ultraviolet radiation ranges from 800 terahertz THz or 1012 hertz to 30,000 THz.

Sometimes the ultraviolet spectrum is subdivided into nearby UV rays ( wavelengths from 380 to 200 nanometers) and extreme UV rays (wavelengths from 200 to 10 nm). The air normally generally opaque to UV below 200 nm (the end of the beam of UV rays); the oxygen absorbs ” light ” in that part of the spectrum of UV rays.

Impact on the environment

In terms of impacts on the environment and human health , it might be useful to subdivide the UV light spectrum differently, for example, into UV-A (“black light” or long wave UV rays with 380 to 315 nm wavelength), UV-B (median wave from 315 to 280 nm), and UV-C (the “germicide” or short wave UV, which ranges from 280 to 10 nm).

The atmosphere of the Earth prevents most UV rays from space reach the ground . The radiation UV-C is completely blocked about 35 km. altitude, due to stratospheric ozone . Most UV-A rays reach the surface, but UV-A rays do little genetic damage to tissues. UV-B rays are responsible for sunburn in sun and skin cancer , even though most is absorbed by ozone just before reaching the surface. The levels of UV-B radiation existing on the surface are particularly sensitive to the levels of ozone in the stratosphere .

The ultraviolet radiation causes burns of skin . It is also used to sterilize glass containers used in medical and biological research.

The term black light

Also known as Black Light (commonly known by its English name “Black light”) is the common name for lamps that emit close ultraviolet electromagnetic radiation , with a very small residual component of visible light. Black light lamps are generally made in the same way as conventional fluorescent lamps , except that they use a single phosphor , and instead of the outer transparent glass they employ a dark glass known as Wood’s glass, which blocks most of the visible light on 400 nanometers.

The ultraviolet radiation from these lamps is produced with a wavelength greater than 350 nm. An ultraviolet wave generated so close to the visible spectrum does no harm (or at least no more harm than visible light can do). However, due to its invisible nature, black light is always used as dim lighting.

Black Light Lamps

These lamps are highly inefficient, emitting few lumen per watt of power, which dangerously increases their temperature , and for this reason it is recommended that they be used for short periods.

Black light is used in dark environments to highlight some colors over others, achieving surprising effects. It is generally accepted that black light only highlights white colors, which have a purplish-white glow, leaving the rest almost in the dark. In fact, black light highlights fluorescent colors, including polyester , which is usually present in white fabrics (in T-shirts, shirts and sneakers). This type of light is usually used in bars and clubs to create a special glow in set with the other lights.

The term ultraviolet (UV) light is applied to electromagnetic radiation emitted by the region of the spectrum that occupies the intermediate position between visible light and X-rays . The ultraviolet spectrum is divided into three designated areas: UV-A, UV-B, and UV-C. The wavelength that causes skin tanning is in the UV-A region. The perception of the human eye begins in violet, at a wavelength of 380 nanometers, (the equivalence of this unit of measurement with the meter is: 1 nanometer (nm) is equal to 0.0000000001 meters), which constitutes the upper limit of the wavelength of the ultraviolet light spectrum.

Germicidal band of ultraviolet light

The band of ultraviolet light that lies between the wavelengths of 200 to 30 nanometers has been called the germicidal region, because ultraviolet light in this area is lethal to all microorganisms. The sunlight through ultraviolet rays emitted destroys bacteria and viruses into streams of water , streams, rivers and storage. Although the sun is an important source of ultraviolet light , much of the transmitted energy does not extend beyond the 295 nanometer wavelength . The shorter wavelengths are absorbed by theozone , the layer that surrounds the globe.

Practical applications of ultraviolet light


The energy ultraviolet be generated by a special germicidal lamp in which the ultraviolet light is emitted as a result of electron flow in a vacuum of ionized mercury between the lamp electrodes. This was accomplished by Anon in 1901 , after Peter Cooper H. invented the mercury arc lamp in the same year.

Germicidal power

Ultraviolet light causes molecular disorders in the genetic material ( nucleic acid , DNA) of the microorganism , this prevents its reproduction and if it cannot reproduce, then it is considered DEAD.

Water purifiers using ultraviolet (UV) light destroy more than 99.9% of bacteria, viruses, and pathogens found in water. No other disinfection medium is as effective as UV light. It does not change the properties of water nor does it affect who uses or drinks it.

Advantages of ultraviolet light

  • They do not affect the ecology , since they do not require the handling or storage of dangerous chemical substances and, of course, they do not cause problems due to overdose.
  • Low initial cost and low maintenance costs compared to other means of water disinfection.
  • Immediate treatment process, no storage tanks or long periods of application to microorganisms are required .


  • Extremely inexpensive, hundreds of liters can be treated for every penny of operating cost.
  • There is no need to add chemical substances to the water so, in addition, it does not generate harmful by-products for health . For example, chlorine plus organic substances produce the dangerous and carcinogenic trihalomethanes.
  • They do not alter the smell, taste, pH, conductivity or general chemistry of [water].
  • Automatic operation that does not require special attention. Just open the water tap.


  • Simplicity and ease of maintenance, periodic cleaning and lamp replacement every ten months, without having moving parts that break down from use.
  • Easy installation, only two connections in the water pipe and one electrical.
  • Fully compatible with other processes such as reverse osmosis, filtration, ion exchange, etc.


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